1. Field of the Invention
The present invention relates to an image forming device.
2. Description of the Related Art
Heretofore, there have been inline inspection devices for offset printing in which, in order to preserve image quality, plural line cameras are provided and images captured therewith are compared with desired original image data. Systems similar to such inline inspection devices are also known in inkjet recording devices.
Inline sensors, large numbers of which are used in offset printing in this manner, may perform sensing with high resolution. However, if a number of sensing pixels is to be increased, it is necessary to increase the number of inline sensors.
In Japanese Patent Application Laid-Open (JP-A) No. 2003-159793, a technology is disclosed that performs calibration of a print head of printing equipment in a short duration. As shown in FIG. 2 of JP-A No. 2003-159793, in this technology, test patterns 92, 94 and 96 are printed on a printing medium 90 using pens 50, 52, 54 and 56, which are ink ejection elements, and these test patterns 92, 94 and 96 are read with an optical scanner 80. This reading is implemented by scanning an effective width of the test patterns 92, 94 and 96 with a single pass of the optical scanner.
In JP-A No. 7-137290, a technology is disclosed that performs recording with different spreading characteristics of inks on recording mediums. In this technology, as shown in FIG. 1 of JP-A No. 7-137290, a test pattern is recorded outside a data recording region 21, an image of the test pattern is sensed, and recording conditions are adjusted in accordance with sensing results.
In JP-A No. 9-141894, a technology is disclosed that reliably detects clogging of nozzles without needing high sensing precision at a sensor, even in a case in which the nozzles have small diameters. In this technology, as shown in FIG. 1 of JP-A No. 9-141894, a nozzle group is divided into plural block units. Ink is blown onto paper 6 by the block units and marks 52 are sequentially formed. Densities of the marks 52 are read by a clogging detection sensor 18. Irregularities at an inkjet head 31 are reported on the basis of whether or not marks 52 of which the read density values are at or below a predetermined value continue for at least a predetermined count.
In recent years, image quality requirements have risen, and qualities of inkjet heads that form images have risen correspondingly. Within individual inkjet modules that constitute an inkjet head (hereinafter referred to simply as modules), impact droplet sizes, direction variations, ejection speeds and timings are substantially uniform. Accordingly, image irregularities within a module are hardly ever seen.
However, inkjet heads are fabricated by repeated lithography of individual modules on wafers. Therefore, sizes thereof are limited by the process. In order to fabricate an inkjet head capable of image formation over the width of a page in one cycle, it is necessary to join and integrate modules fabricated by processing on wafers, and form the modules into an inkjet head bar for image formation.
In the current circumstances, image irregularities within modules are not a problem. However, positional offsets when modules are joined and differences in impact droplet sizes, impact droplet speeds and timings between modules, which cause image irregularities, still occur. As things stand, conventional sensors are not capable of sensing positional offsets at joins of modules.